1. Field of the Invention 
This invention relates to earthquake locks for cabinets and particularly to earthquake locks for cabinets using magnetic latches. 
2. Description of the Prior Art 
Earthquakes have been a part of the world since the beginning of time. They are cause of much destruction. Most earthquakes however are not catastrophic events. These minor earthquakes may still cause damage as items are thrown off shelves and contents of closed cabinets are discharged into the room. Not much can be done to protect items stored on open shelves. However, closed cabinets have doors that, if they were to remain closed in an earthquake would prevent a lot of incidental damage. To that end, several types of “earthquake lock” have been invented that allow normal use of cabinets under ordinary circumstances, but act to lock the cabinets doors shut in the  event of seismic activity. U.S. Patents that address this problem are U.S. Pat. Nos. 5,152,562 and 5,518,282. U.S. Pat. No. 5,152,562 teaches a device that uses a ball that is held in an elevated position in a housing. At the base of the housing is a latch that attaches to the inside of a cabinet door. The latch has a slot cut into it such that when the door is closed, the slot is positioned under the ball. When an earthquake strikes, if the force is sufficient, it causes the ball to be pushed from its resting position and down into the slot. This then prevents the door from opening and spilling the contents of the cabinet. Although this system appears to work, it has several problems. First, the ball is set in a recess. Although the sensitivity of the device can be adjusted, it can take considerable force to cause the ball to drop. Second, the latch with the slot is attached to the door. If the movement that causes the ball to fall also causes the door to fly open, the ball will not fall into the slot. If the door has opened widely enough, it may even block the door from closing again. Finally, once the lock is set, there is no way to open the cabinet again. The patent teaches securing a string that passes through the side of the cabinet so that a user can pull the ball back up so that the door can be opened. 
U.S. Pat. No. 5,518,282 teaches a system that keeps a door or drawer locked all the time. In this way, an earthquake cannot cause the door to open. Moreover, because the door is locked al the time, there is no need for a system to cause the door to be locked, with the inherent possibility of the failure of the system. The patent uses a hooked shaped latch that hooks onto a ledge attached to the door. There is a release mechanism provided that allows the door to be opened for ordinary use. While this  device eliminates the need for a device to lock the door in the event of an earthquake, it has the problem of prevent easy access to the contents of the cabinets. Because earthquakes rarely occur but accessing the cabinets is a daily occurrence, this system rapidly becomes a nuisance. 
Two systems have been developed in Japan as well. JP9067970A2 and JP9078926A2 use balls to engage latches to prevent doors from opening in the event of an earthquake. JP9067970A2 teaches a system similar to U.S. Pat. No. 5,152,562 in that a ball is designed to drop into a bracket with a slot, which is attached to the door. JP9078926A2 teaches a system in which a ball drop down and engages a spring mechanism that causes two pins to laterally move into holes drilled in the doors. Once the pins are in place, the doors will not open. These systems suffer from the same problem as discussed above: if the doors are open at the same time the ball drops, the ball does not align with the slot in the bracket in the first case, or what is worse, the pins will not align with the holes in the doors in the latter case. This is worse because one the pins have been deployed, the doors will not close fully. Thus, when the next jolt hits, the doors may be flung open, with the locks having no effect. 